Photochemistry of functionalized diphosphiranes

The structure of the functionalized trans-diphosphiranes 1a-e, obtained by reaction of halogenocarbenes with the trans-diphosphene is confirmed by X-ray diffraction. The photolysis of 1a-e lead to the functionalized cis- and trans-1,3-diphosphapropenes 2a-e as major products, via the diphosphiranyl and the diphosphapropenyl radical intermediates. The latter are characterized by ESR spectroscopy using the spin-trap method. The trans configuration of 2a is also confirmed by X-ray diffraction. The mechanism of the ring-opening, involving P-P bond rupture, is discussed